Viewpoint: standard set for compressor efficiency

The European Union is becoming increasingly concerned about the challenges faced by member states from their dependence on energy imports, scarcity of supply and the need to limit climate change.

As a consequence, a new directive (2012/27/EU) has been issued on energy efficiency, from which the UK government has implemented Articles 7 and 8: the Energy Efficiency Obligation Scheme (EEOS) and the Energy Saving Opportunities Scheme (ESOS).

For end-users of compressed air systems, this legislation throws a spotlight on energy efficiency. However, with so many factors to consider – from energy consumption to air leakage – it can be hard to assess the real running costs of a compressor.

With this in mind, BCAS instigated the BS IS0 11011 standard, adopted as the International Standard ISO 11011, which sets out a process-specific standard for the assessment of a compressed air system.

Be prepared

The standard identifies the roles and responsibilities of those involved in the assessment and categorising of compressed air systems into three functional subsystems.

First is supply, which includes the conversion of the primary energy source to compressed air energy. Second is transmission, which takes account of the movement of compressed air energy from where it is generated to the point of use. Finally, there is the installation’s demand for air, including the total of all compressed air consuming products for both end-use applications and compressed air waste.

This approach provides a structured framework for a full system assessment, and then the subsequent reporting and documenting of findings. In doing so, it will identify any estimated energy savings helping operators to reduce costs and improve performance.

The standard identifies the roles and responsibilities of those involved in the assessment and categorising of compressed air systems

Clearly, not all compressed air systems are the same. Some may vary in terms of age, application, size or location, so the requirements for assessment will vary.

To compensate for this variety, the standard also identifies the relevant methodologies that should be used for assessment, which might include observation and research, spot check measurements or data logging, including real-time trend analysis.

This means that plant engineers or service providers can use the most appropriate methodology, either in part or full. So, for example, it may not be necessary to carry out extensive data logging if simple observations and existing data are enough to complete the assessment.

Whole system approach

As with any industrial process analysis, factoring in a whole system approach, rather than concentrating on select, individual components, will enable a more comprehensive understanding of the energy performance of the installation.

Typically this process would start with defining the scope of a full assessment of the system. This could include areas such as compressed air use, production functions, leaks, poor performance, compressed air demand and utility bills.

As with any industrial process analysis, factoring in a whole system approach, rather than concentrating on select, individual components, will enable a more comprehensive understanding of the energy performance of the installation

Data and observations can then be collected from each area, assessed and remedial or upgrade work undertaken to deliver improved cost efficiencies.

For example, the findings might be used to determine the air leakage rate. A leak of just 3mm could cost a business more than £700 a year, but with some small improvements, these leaks could be rectified, saving considerable cost.

Elsewhere, the assessment may help to identify if the right compressor and/ or air receiver is being used, whether the system pressure is unnecessarily high, compared to the site’s actual demand, or whether the air is being over-treated.

• Dean Abbott is technical officer at BCAS.